In order to protect humans against smoke or fire which may erupt in a variety of building structures, and particularly in large office buildings, hotels, and the like, many different types of shielding devices have been developed over the years which are operative to seal off certain exit and entrance ways through which smoke is likely to travel. As is well known, many fire related deaths are the result of smoke inhalation, so there have been various different approaches proposed to rapidly sealing off areas adjacent to which smoke is likely to travel very swiftly once a fire anywhere in that path has been started. An example of one such path is that defined by an elevator shaft which creates a low resistance and sometimes well drafted and well defined large area path for smoke to travel and become rapidly drawn into any opening into the path between floors of a building.
Examples of such prior patented approaches to sealing off certain exit and entry ways, such as elevator doors, are disclosed in U.S. Pat. No. 2,947,239 issued to Burgess, U.S. Pat. No. 3,807,480 issued to Smart, U.S. Pat. No. 3,960,216 issued to Isobe, in U.S. Pat. No. 4,971,994 issued to Ho and in U.S. Pat. No. 4,766,958 issued to Mitchel, all incorporated herein by reference.
Other prior approaches to sealing off elevator doors and other selected entrance and exit ways for the purpose of smoke isolation in case of fire include horizontally and vertically driven sliding doors and spring biased doors of various types. These latter types of prior art elevator sealing approaches have exhibited many operational disadvantages and have been difficult to economically manufacture and maintain. In addition, many of these schemes not directly located at an elevator door require the dedication of valuable floor space on one or both sides of the elevator lobby which cannot be used for other office purposes.